1. Field of the Invention
The present invention relates to a resin molding method of a semiconductor device utilizing a semiconductor element, such as a light emitting element or a light receiving element, in particular, to a technology for high quality transfer molding wherein resin burrs do not occur at the time of transfer molding using a resin material for covering a package wherein a light emitting element is mounted.
2. Description of the Background Art
A transfer molding method has been utilized as a method for sealing an LED chip in a resin mold. According to this method, which is a resin molding method of a semiconductor device, a semiconductor element is mounted on a lead frame, and this semiconductor element and lead electrodes are connected so that, in the resulting state, a space that includes this semiconductor element is formed by engaging an upper die and a lower die and, after that, resin is injected into this enclosed space so as to cover the surface of the lead electrodes and, then, the semiconductor element is sealed into resin when the resin is hardened.
Furthermore, such a transfer molding method includes a method for preventing resin burrs on lead electrodes wherein a die is made to make contact with the lead electrodes provided on a rigid substrate made of glass epoxy, or the like, and resin is injected through a gap created between the die and the substrate so that the resin is prevented from leaking out onto the surface of the lead electrodes (see, for example, Japanese unexamined patent publication H8 (1996)-148724).
In addition, a light emitting element is mounted on the bottom surface of a recess, created so that the opening becomes broader closer to the top, in order to increase the output efficiency of the light that has been emitted from the light emitting element, and the positive and negative electrodes of the light emitting element are connected to lead electrodes for supplying power to the light emitting element through wires and, after that, a mold is formed so as to seal the light emitting element in resin.
According to a method for injecting resin by utilizing lead electrodes, however, excess portions of a mold occurring when resin moves into a gap between dies, creating so-called resin burrs, cannot be completely prevented. According to a method wherein a die is made to make contact with lead electrodes provided on a rigid substrate made of, for example, glass epoxy, or the like, a slight gap occurs between the mold and the lead electrode and, when mold material having great fluidity is made to flow into the die, the material leaks out, even from the slight gap, onto the surface of the package and onto the surface of the lead electrodes causing the occurrence of resin burrs. The external appearance of the light emitting device is negatively affected due to resin burrs occurring in the manner and, in addition, these resin burrs become a hindrance at the time when the electrodes are processed in subsequent steps. Thereby, the task of shaving off the resin burrs with a file, or the like, becomes necessary and such task of removing the resin burrs takes much time and effort. Therefore, it is necessary to follow a method wherein no resin burrs occur in the formation process of a mold material.
In addition, in the case that a light emitting element is mounted on the bottom surface of a recess, created so that the opening becomes broader closer to the top in order to increase the output efficiency of the light emitted from the light emitting element, and, then, a mold member is formed over the light emitting element, the mold member after formation has a convex form that protrudes inward toward the package and, therefore, the mold portion is easily removed from the package and problem arises wherein a light emitting device of a high reliability cannot be formed.